On-Chip Smart Temperature Sensors for Dark Current Compensation in CMOS Image Sensors

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2 Citations (Scopus)

Abstract

This paper proposes various types of on-chip smart temperature sensors, intended for thermal compensation of dark current in CMOS image sensors (CIS). It proposes four different architectures of metal-oxide-semiconductor (MOS)-based and bipolar junction transistor (BJT)-based temperature sensors inside and outside the CIS array. Both of the MOS-based temperature sensors make use of the thermal dependence of MOS transistors working in the subthreshold region with ratiometric currents and are quantized by the 14-bit first-order incremental delta-sigma analog-to-digital converters (ADCs). Fabricated using 0.18- CIS technology and measured on four chips, the proposed temperature sensors are compared, on their resolution and process variability, as well as on their effects on the neighboring image pixels implemented on the same chip. Experimental results show that the MOS-based temperature sensors inside and outside the array consume a power of 36 and 40ext{W} , respectively, both achieving 3-sigma (sigma ) inaccuracy less than ±0.75 °C on four different chips, over a temperature range from -20°C to 80 °C at a conversion time of 16 ms. The temperature sensors facilitate the digital thermal compensation of dark current in the CIS array, by at least 80%, in experiments.

Original languageEnglish
Article number8723532
Pages (from-to)7849-7860
Number of pages12
JournalIEEE Sensors Journal
Volume19
Issue number18
DOIs
Publication statusPublished - 2019

Keywords

  • CMOS image sensor
  • dark current
  • process variability
  • Temperature sensor
  • thermal compensation

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